Skin is the “window” to the body. Skin is unique among the body's organs for several reasons: (1) skin is the largest organ of the human body; (2) skin is directly exposed to the environment; (3) skin is an excellent excretory organ; (4) skin is the most visible and accessible organ of the body; and (5) skin is a highly active immune organ of the body.
Skin has another important quality: The molecular profile of skin has information that is valuable for physiological monitoring of, among other things, small organic molecules, proteins, DNA, RNA, and lipids. Much can be learned from skin's molecular profiling. For example, pathogens (e.g., bacteria) that grow on skin may allow for forensic identification. Skin's molecular profile may reveal environmental factors to which the body has been passively exposed. These environmental factors may range from the mundane, e.g., allergens, toxins, and cosmetic products, to the industrial and/or agricultural, e.g., industrial solvents, fertilizers, and pesticides, to the dangerous, e.g., explosives and other warfare agents.
Skin's molecular profile may also reveal factors to which the body has been actively exposed. More particularly, skin's molecular profile may reveal what the body has consumed. For example, abused substances (e.g., illegal drugs or narcotics) and therapeutic drugs (e.g., tramadol, fluconazole, barbitals, and anabolic steroids) may be found in skin for weeks after consumption.
Skin's molecular profile may also aid in the diagnosis of conditions and diseases. For example, skin cholesterol is a proxy of the extent of arterial blocks. Glycation of skin collagen is an indicator of a history of diabetes. Skin deposition of β-amyloids may indicate the existence and extent of Alzheimer's disease. And skin globular proteins (e.g., IgE) may indicate allergies to specific allergens.
Several methods exist for sampling biomolecules from skin. For example, one current method is skin biopsy. However, skin biopsy is invasive and analysis is difficult. Practically speaking, skin biopsy is designed for well-equipped experts and, thus, its use in a point-of-care setting is limited. Another current method for sampling biomolecules from skin, tape stripping, suffers from these same limitations and is generally unacceptable because of variability in results. Yet another current method for sampling biomolecules from skin is taking a skin swab. While desirable because of its simplicity, a skin swab is superficial in its depth of inspection, and qualitative in its results. Finally, tissue has been subjected to ultrasound in the presence of surfactants such as sorbitans (“SPANs”), polyoxyethelene sorbitans combined with fatty acids (Tween® surfactants), cetyl trimethylammonium bromide (“CTAB”), and their mixtures. See U.S. Pat. No. 6,589,173 issued to Mitragotri et al. However, SPANs, Tween® surfactants, and CTAB, individually and collectively, have been found to be unsuitable to recover skin constituents. Sorbitans and Tween® surfactants, which are nonionic surfactants, are mild and non-denaturing in character, but are ineffective to solubilize skin tissue. CTAB, a cationic surfactant, is effective to solubilize skin tissue, but unsuitably denatures proteins, profoundly changing properties of biomolecules in solution, rendering them unusable for functional purposes.
Thus, a need exists for compositions for skin sampling, as well as for mucosal membrane and other tissue sampling, which, when used in conjunction with applied energy, at least partially solubilize such skin, mucosal membrane, and other tissue. A further need exists to preserve the functionality and structural integrity of analytes, including biomolecules, obtained from the solubilized skin, mucosal membrane, and other tissue. A related need exists to remove surface lesions from skin and mucosal membranes, while preserving biomolecules obtained from the lesions for diagnosis or prognosis.
A further need exists for compositions and methods for solubilizing cells and other tissues (e.g., skin, liver, heart, brain, and other organs), and for the recovery of proteins, including cytosolic proteins, from the solubilized cells and tissues. Finally, a need exists for compositions and methods for fast and efficient solubilization and isolation of phosphoproteins from skin.